CUSTOM SYSTEMS ::: Stack Router Cell
This stack router cell stands as a benchmark in sheet metal production. This machine was delivered above and beyond the customer’s strictest specifications. Many things about this cell are innovative, including the router itself. This system enables a single operator to safely handle the very large sheet metal parts without damage, as compared to as many as six people previously required.
The production process begins with part orders in the customer’s database. We worked closely with Northrop Grumman Information Technology (NGIT) to integrate our software with their Enterprise. NGIT provides Information Technology services for Vought Aircraft Industries, where the cell is installed.
Each part in the system has a geometry file containing tolerances, material requirements, grain constraints, and part quantity. With minimal human intervention, our custom software loads orders and organizes them into similar sheet materials and thicknesses. It then optimizes and pre-nests to maximize material usage and minimize cutting time. Sheets can be up to 4ft x 12ft and stacked as high as 0.5”. Once the nests are pre-nested, the system automatically generates a report so material can be ordered from Alcoa quickly and accurately.
Material is delivered to Vought with bar codes attached to the top sheet of each nest on pallets containing approximately one shift’s production. The pallets are loaded onto a material cart with a forklift, which is conveyed under the robot. The robot scans the bar code for the nest ID. The system immediately queries Vought’s database which tells it how many and what size sheets are in the nest for stacking. The optimizing is performed and the part program generated automatically and sent to the router control. A graphical representation of the nest is also sent to the Nestviewer monitor located above the unload table. The robot can separate thin sheets to avoid stacking too many or damaging material. The sheet edges are located with sensors, and the sheets are stacked even and square, even though they may be misaligned up to 3” on the material pallet. The robot stacks each nest onto a sacrifice sheet, and loads the completed stack completely onto the router bed. No operators are required to load material onto the machine.
The part program is automatically loaded into the control PC on the stack router and powerful table clamps secure the material in place for cutting. The router is a direct drive machine capable of 0.6G accelerations, 5,000 in/min traverse speeds, and 0.0002” accuracy across the entire table. The spindle is 30,000 rpm with HSK tooling. The spindle and linear motors are liquid cooled. It has an integrated servo driven tool drawer that holds 48 tools. The drawer also contains a tool laser for broken tool detection, length offsets, and radius offsets. Each pocket in the tool drawer has a sensor to detect misplaced tools and to avoid double stacking of tools.
Once the material is loaded, the machine first drills all holes required, then begins the routing process. To keep the parts in place, the machine leaves micro-tabs to hold the parts in place. A unique presser foot was created to hold down the material without scratching the surface or applying a side load to the material during cutting. A powerful chip collection system keeps the area clean and dust free and separates the aluminum chips from any dust picked up from the MDF sacrifice sheet. After the parts are routed, the tabs are cut free using a detab process and a tab foot that holds parts as small as 1” square. No rivets or screws are need to cut even the smallest parts.
Once the detab process is complete, the finished nest with loose parts is automatically conveyed to the unload table. Individual part numbers can be selected on the Nestviewer located above the unload table, selected parts are displayed in green, unselected parts in red. The scrap material is discarded, and the sacrifice sheet is sent along conveyors back to the robot for successive nests. The sheets can be reused until the surface is too uneven to support new material, at which point the sacrifice sheets can be flipped on the powered flipper table.
Each nest is stacked while the previous nest is being cut. While the finished parts are being unloaded by the operator the next nest is being ran, maximizing productivity.
The Stack Router Cell, like all of our systems, can be modified to fit your specific application. For example, another customer had a requirement for a stack router with sheet sizes up to 6’ x 24’. They also wanted to eliminate having to manually screw the sheets to a wood table like on their existing machine, which our micro-tab system provides.
To meet this customer’s needs we increased the XY travels of the router. By using linear motors and scales axis length is practically unlimited and accuracy is not compromised even with very long travels. A three axis powered gantry crane design was modified to provide an inexpensive platform for moving the large pallets. Modifications to the crane include specially designed guides and rails which provide lateral rigidity of the end effector.
Then we designed the router table to accommodate a pair of 2” x 6’ x 24’ aluminum pallets. These pallets are transported on and off the bed of the router with the crane and enable near continuous operation of the router while the sheets and parts are loaded and unloaded on adjacent tables. Manually adjustable clamps sliding in T-slots allow for 1’-6’ wide and 2’-24’ long sheets. The result is an automated system which enables a single operator to safely handle the very large sheet metal parts without damage, as compared to as many as six people previously required.
